The invention relates to a pressure transducer for use in medical technology.
Tube pumps are utilized with great frequency for the transport of fluids for irrigation of body cavities, e.g. in endoscopic treatment processes. The tube system required for operation in such pumps, which system must be sterile, is designed either to be sterilizable and reusable or as a disposable tube set.
Such a tube kit comprises:
(a) a connection to a storage container (frequently a bag),
(b) a pump segment of a silicone hose which is inserted in a tube pump,
(c) a connection to a pressure sensor,
(d) a relief valve providing passive safety,
(e) a connection to a trocar or endoscope.
For separating the sterile interior of the tube set from the unsterilized pressure sensor it is known to use a "Millipore" filter wherein pressure measurement takes place indirectly by way of an air column. This solution has the following drawbacks in practical usage:
If the tube leg provided for the pressure measurement is not attached in time, or is attached incorrectly to the pressure pickup connection, then, on the one hand, a pressure measurement is impossible; on the other hand, liquid can rise in this tube leg and wet the air filter, thereby falsifying the pressure measurement, in certain cases even without being noticed, because then a pressure measurement via the air column is no longer possible. Furthermore, there is then also the possibility of liquid escaping from the pressure pickup connection.
Moreover, the use of a so-called pressure dome has likewise been known from the prior art:
In this case, a pressure dome containing a flexible diaphragm is connected to the tubing. This flexible diaphragm seals off the tubing. The pressure dome is connected to an unsterilized pressure sensor, for example, by means of a bayonet catch.
The pressure dome normally has two connections and a chamber sealed ,off by a diaphragm. The diaphragm is tensioned by way of a pressure pickup, thus permitting the pressure measurement within the sterile interior. The diaphragm must be of such a design that, if at all possible, it does not falsify the measurement, i.e. it must be sufficiently resilient with respect to the stiffness of the pressure pickup diaphragm. One connection serves for joining to the monitored tube system (for example infusion hose kit, catheter); the other one is utilized for venting purposes during the initial filling of the entire system.
The conventional pressure domes thus are located at the end of a side branch of the tube kit and permit pressure measurement within this tube kit (blood, infusion solution) while avoiding a coupling air cushion and/or the use of a sterile pressure pickup.
As for the state of the art, attention is invited, as a supplement, to the published patent disclosures DE 29 30 869 C3, DE 35 10 043 C2, and EP 0 208 955 A1; express reference is had to these disclosures, by the way, for an explanation of all terms not elaborated on in detail herein.
Furthermore, the relief valve is designed as a sterilizable, reusable part and, in the conventional systems, must be additionally incorporated into the tube system, for example by cutting the tubes open. This means that in case of user negligence the valve is not connected. Under excess pressure, the liquid will pass to the outside.